Elements & The Periodic Table Chapter 3 Elements & The Periodic Table

Section 1 Introduction to Atoms Matter Anything that has mass and takes up space. Atom-basic part of matter Atom means indivisible (can’t be divided) in Greek. Atomic Theory-atoms are the building blocks of matter.

Structure of the Atom Made up of 3 small parts. 1. Protons 2. Neutrons 3. Electrons

Protons Found in the nucleus Have a positive charge (+)

Neutrons Also found in the nucleus No charge- neutral

Electrons Found on energy levels outside the nucleus. Has a negative charge (-) Electrons are the smallest part of an atom. Found on energy levels Also known as energy rings/electron cloud

Energy Levels of Electrons Surround the nucleus. The number of electrons on each energy level are: 2,8,18,32,32,18,8,2 Must fill up energy ring before going to the next ring. Last ring are valance electrons.

Mass of an Atom (Atomic Mass) Equal to the number of particles in the nucleus. Protons + Neutrons = Mass

Atomic Number The number of protons AND the number of electrons. Protons and electrons are always the same number.

Atoms and Elements There must be an equal amount of positive and negative charges. Because of this…… ATOMS ARE ALWAYS NEUTRAL, THEY HAVE NO CHARGE.

Mass Number and Isotopes Isotopes-atom of the same element with a different number of neutrons. Isotopes that are in nature are unstable. They are radioactive The number of neutrons does not affect the charge, only the mass. The mass number helps tell one isotope from another.

Example of Isotopes

Section 2-Organizing the Elements Periodic-to have a regular repeating pattern. Dmitri Mendeleev- created the first periodic table Ordered the table from lowest to highest mass (Big Problem)-they all didn’t fit in the right spots.

Henry Moseley- arranged the elements in order of increasing atomic number. He designed the modern periodic table. He discovered this pattern had no irregularities.

Columns and Rows Columns (groups)-represent elements with similar properties and electron arrangements. Rows (periods)-represent increasing atomic number, go from metals to nonmetals.

Section 3-Metals Properties of Metals: Luster: Surface will reflect light (shiny) Conduct heat and electricity Useful to make cooking utensils and wire High melting point (except pure gold and pure silver) because they are soft metals. Pure gold and pure silver are not used alone in jewelry and coins, they are combined. Gallium melts at room temperature. Mercury is a liquid at room temperature.

Malleability Most useful property of a metal. Can be flattened, bent, and shaped without breaking. Ductile-can be pulled into wire.

Alkali Metals: Group 1 Li, Na, K, Rb, Cs, Fr Most reactive Combine very easily with other elements All have one electron in the outer shell Found in nature ALWAYS found in compounds Combine to form salts Soft and easily cut with a knife Low density Melt at low temperatures

Alkaline Earth Metals: Group 2 Reactive, but not as reactive as group 1 2 valence electrons Occur in nature and combine with other elements Magnesium and calcium are the most common Calcium makes up bones and teeth Used for building materials such as cement. Used for medicine-Magnesium hydroxide-milk of magnesia used for upset stomachs

Transition Metals Most of the elements fall into this group Hard and shiny High melting point Good conductors of electricity Less reactive, but can combine with other elements Fe, Co, Ni are magnetic Found in ores-minerals containing large amount of metal compounds

Rare-Earth Metals Separate rows at the bottom of the periodic table Lanthanides Elements 58-71 except 61 occur in nature Occur in small amounts in the earth’s crust Small amounts are used in lasers Create the red color in TV

Other Actinides-the rest of the periodic table Man made (Synthetic)

Nonmetals Properties No luster Poor conductors Dull and brittle Many are gases at room temperature Have many electrons in their outer shell Located to right of the zigzag line

Metalloids Properties Shiny, but not much luster Conduct heat and electricity, but not as good as metals Semiconductors-Ex. Silicon will conduct electricity only at certain temperatures.

Boron Group Only element in group 13 that is not a metal Brittle black metalloid Aluminum is the most abundant metal on Earth.

Carbon Group Only nonmetal in group 14 Found in ALL living things 2 forms: Graphite (pencils) Diamonds

Nitrogen Group Only gas in group15 80% of the air we breathe Essential to living things and for making proteins

Oxygen Group Only gas in group 16 Most abundant element on Earth Most important element

Halogen Group Known as salt formers Elements in group 17 Found in most foods that we eat Combine with metals to form salts What metals do they combine with?

Noble Gases Group 18 Contains 6 colorless gases DO NOT combine with any other elements All exist in the Earth’s atmosphere

Hydrogen Properties do not fit with any other group Reacts easily with other elements Can act as a metal or a nonmetal